Optimising Transformer Performance At A 5MW Industrial Solar Park

OrxaGrid partnered with a solar operator that wanted to reduce operating costs through predictive maintenance

About Solar Farms and Transformers

Solar power in India is a fast developing industry. India is one of the lowest cost producers of solar due to combination of high solar potential, low land costs and dropping panel costs.

Most solar energy in India is generated by large-scale industrial solar farms which feed into the local electricity grid. A 5MW solar farm can power over 1,500 homes annually (based on an average annual consumption of 3,300 kWh of electricity for a house) and save 2,150 tonnes of CO2.

Solar farms do not have moving parts, and maintenance is minimal compared to other electricity generation types but large scale solar installations need efficient transformers to feed the generation of electricity into the electricity network. Power transformers are critical grid assets delivering electricity at voltage rating required to power residential, industrial, and commercial users. As such power transformers are single points of failure and therefore it is critical that power transformers operate at high efficiency and reliance.

The Challenge

Typically, most solar operators follow routine maintenance checks on their transformers which is not only time consuming but also expensive due to personnel cost and loss of revenue during down time. Routine maintenance prevents operators from predicting future transformer failures, inefficiencies, and maximum permissible utilisations. It may also result in deterioration of nearby assets that are overloaded during this time to manage the increased demand transfer. Realising the importance, the partner tasked OrxaGrid with monitoring and analysing a 1.5MVA step up transformer that fed electricity from the 5MW solar plant into the electricity grid.

Partner Requirements

The objective of the project was to create a system that would allow the industrial operator to monitor and analyse its transformers to ensure a smooth and efficient inflow of energy from the solar generation site.

To do this, the operator needed a system that fit the following criteria

• Electrical parameters of transformers in real-time.

• OLTC tap position indicator which can be accessed from the control office.

• Monitoring of Alarm and Shutdown Signals

• Monitoring oil and winding temperatures and oil levels

• Identifying and predicting energy violations such as over voltage, phase imbalance and excessive peak demands

• Monitoring the condition of transformers to reduce maintenance downtimes

All of this information needed to be presented in an easy to read dashboard that can be accessed online or anywhere.

Solution

OrxaGrid deployed its unique Analytics Platform to analyse the solar generation data at the transformer location. The system constituted STEM sensors for data collection and analytics platform for data management, analysis and visualisation.

STEM was installed on the transformer to measure transformer power parameters as well as transformer condition. The sensor communicated through HTTPS REST services using secure Machine to Machine cellular cards to the Analytics Platform. Additionally, STEM stored backup data onboard for extra reliability. OrxaGrid enforced security using device specific logins to prevent unauthorised access and SSL Encryption for secure data transfer. The web and mobile enabled dashboards were designed to be intuitive and simplicity driven for use by both domain experts and non-technical users of the utility.

Result

The project return on investment was apparent within days of implementation. Key results were:

• Identified daily peak loading on transformer at noon and moving to zero at night. Correlation between solar generation and weather information such as cloud cover was observed

• Solar generation during the summer and winter months was almost 50% more than the cloudy rainy season

• Voltage drops appeared at evening times when solar generation stopped as the asset tries to synchronise with the grid network

• Voltage levels were closely monitored to ensure they remained within permissible limits and thus prevented technical losses

• Transformer tap positions were recommended to be changed automatically based on solar generation prediction

• Continuous energy accounting identified that power generated from the solar park was equivalent to power supplied to the grid and that the internal transformer losses were minimal

• The transformer had adequate spare capacity and due to the low loading, its long-term healthiness showed reliable results

OrxaGrid’s IoT based solution proved to be a viable solution to the industrial solar park for maximising energy efficiency of the solar feed into the grid. The system was scalable through retroactive addition of sensors from other substations in other divisions of the utility. The system was also interoperable with existing data sources such as metering and SCADA.

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